uk.ac.starlink.votable

Class VOElementFactory

java.lang.Object

uk.ac.starlink.votable.VOElementFactory

public class VOElementFactory
extends java.lang.Object

Provides methods for constructing VOElements from a variety of sources. A VOElement can be made either from an existing DOM Element or from some non-DOM source such as a file, input stream, or SAX stream. In the latter case a DOM is built using the transformToDOM(javax.xml.transform.Source,boolean) method with no validation. There are several optimisations performed by this method which distinguish it from a DOM that you'd get if you constructed it directly; the most important ones are that the data-bearing parts (children of STREAM or TABLEDATA elements) of the XML document are not included in the built DOM, and that any reference to the VOTable DTD is resolved locally rather than making a potential network connection. You almost certainly don't need to worry about this; however if for some reason you want to work on a 'normal' DOM, or if you want validation, you can construct the DOM yourself and invoke one of the non-transforming makeVOElement methods on the result.

The various makeVOElement methods may return an object of class VOElement or of one of its subclasses, according to the name of the element in question; specific subclasses are provided only where some extra functionality is available, for instance the TableElement.getData() method of the TableElement class. One upshot of this is that a tree of VOElements need not conform to the VOTable DTD, elements of any name may be in it. Wherever an element has a name which matches an element with specific significance in a VOTable document however, such as "TABLE", it is handled accordingly.

Field Summary

Fields

Modifier and Type	Field and Description
static boolean	STRICT_DEFAULT Determines whether the default strictness state is true or false when the STRICT_PROPERTY property has not been set.
static java.lang.String	STRICT_PROPERTY Property which determines the default strictness state.

Constructor Summary

Constructors

Constructor and Description
VOElementFactory() Constructs a new VOElementFactory with the default storage policy.
VOElementFactory(StoragePolicy policy) Constructs a new VOElementFactory with a given storage policy.

Method Summary

Modifier and Type	Method and Description
StoragePolicy	getStoragePolicy() Returns the storage policy currently in effect.
boolean	isStrict() Indicates whether a strict reading of the VOTable standard is in effect.
static boolean	isStrictByDefault() Indicates whether strict interpretation of the VOTable standard is on by default (if it has not been set explicitly).
VOElement	makeVOElement(DataSource datsrc) Builds a custom DOM read from a DataSource and returns a new VOElement based on its top-level element.
VOElement	makeVOElement(org.w3c.dom.Document doc, java.lang.String systemId) Returns a new VOElement based on a DOM Document node.
VOElement	makeVOElement(javax.xml.transform.dom.DOMSource dsrc) Returns a VOElement based on a DOM source.
VOElement	makeVOElement(org.w3c.dom.Element el, java.lang.String systemId) Returns a VOElement based on a given DOM element.
VOElement	makeVOElement(java.io.File file) Builds a custom DOM read from a file and returns a new VOElement based on its top-level element.
VOElement	makeVOElement(java.io.InputStream strm, java.lang.String systemId) Builds a custom DOM from an input stream and returns a new VOElement based on its top-level element.
VOElement	makeVOElement(javax.xml.transform.Source xsrc) Returns a VOElement based on an XML Source.
VOElement	makeVOElement(java.lang.String uri) Builds a custom DOM read from a URI and returns a new VOElement based on its top-level element.
VOElement	makeVOElement(java.net.URL url) Builds a custom DOM read from a URL and returns a new VOElement based on its top-level element.
void	setStoragePolicy(StoragePolicy policy) Sets the storage policy.
void	setStrict(boolean strict) Determines whether a strict reading of the VOTable standard will be enforced.
javax.xml.transform.dom.DOMSource	transformToDOM(javax.xml.transform.Source xsrc, boolean validate) Gets a custom DOMSource from a generic XML Source.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

STRICT_PROPERTY

public static final java.lang.String STRICT_PROPERTY

Property which determines the default strictness state. Its value may be set to "true" or "false" case-insensitively. If unset, the default will be determined by the value of STRICT_DEFAULT. The return value of the isStrict() method will be set like this unless strictness is set explicitly.

See Also:

setStrict(boolean), Constant Field Values

STRICT_DEFAULT

public static boolean STRICT_DEFAULT

Determines whether the default strictness state is true or false when the STRICT_PROPERTY property has not been set. True by default.

Constructor Detail

VOElementFactory

public VOElementFactory(StoragePolicy policy)

Constructs a new VOElementFactory with a given storage policy. The StoragePolicy object is used to determine how row data which is found within the DOM will be cached.

Parameters:

policy - storage policy

VOElementFactory

public VOElementFactory()

Constructs a new VOElementFactory with the default storage policy.

See Also:

StoragePolicy.getDefaultPolicy()

Method Detail

getStoragePolicy

public StoragePolicy getStoragePolicy()

Returns the storage policy currently in effect. This is used to determine how row data found in the DOM will be stored.

Returns:

current storage policy

setStoragePolicy

public void setStoragePolicy(StoragePolicy policy)

Sets the storage policy. This determines how row data found in the DOM will be stored.

Parameters:

policy - new storage policy

makeVOElement

public VOElement makeVOElement(org.w3c.dom.Element el,
                               java.lang.String systemId)

Returns a VOElement based on a given DOM element. The systemId is also required since some elements (STREAM, LINK) may need it for URL resolution. It may be null however (which is fine if there are no relative URLs used in the document). If el is already a VOElement, it is just returned.

Parameters:

el - DOM element on which the new object will be based

systemId - the location of the document

makeVOElement

public VOElement makeVOElement(org.w3c.dom.Document doc,
                               java.lang.String systemId)

Returns a new VOElement based on a DOM Document node. The systemId is also required since some elements (STREAM, LINK) may need it for URL resolution. It may be null however (which is fine if there are no relative URLs used in the document).

Parameters:

doc - DOM document node

systemId - the location of the document

Returns:

VOElement based on doc

makeVOElement

public VOElement makeVOElement(javax.xml.transform.dom.DOMSource dsrc)

Returns a VOElement based on a DOM source.

Parameters:

dsrc - DOM source representing an Element or Document node

Returns:

VOElement based on dsrc

makeVOElement

public VOElement makeVOElement(javax.xml.transform.Source xsrc)
                        throws org.xml.sax.SAXException,
                               java.io.IOException

Returns a VOElement based on an XML Source. If the source is a SAX or Stream source, this will involve a parse.

Parameters:

xsrc - the XML source representing the element

Returns:

VOElement based on xsrc

Throws:

org.xml.sax.SAXException - if xsrc is not a DOM source and there is a parse error transforming it to a DOM

java.io.IOException - if xsrc is not a DOM source and there is an I/O error transforming to a DOM

makeVOElement

public VOElement makeVOElement(java.io.InputStream strm,
                               java.lang.String systemId)
                        throws org.xml.sax.SAXException,
                               java.io.IOException

Builds a custom DOM from an input stream and returns a new VOElement based on its top-level element. The systemId is also required since some elements (STREAM, LINK) may need it for URL resolution. It may be null however (which is fine if there are no relative URLs used in the document).

Parameters:

strm - stream containing XML data

systemId - the location of the document

Returns:

new VOElement

Throws:

org.xml.sax.SAXException

java.io.IOException

makeVOElement

public VOElement makeVOElement(java.lang.String uri)
                        throws org.xml.sax.SAXException,
                               java.io.IOException

Builds a custom DOM read from a URI and returns a new VOElement based on its top-level element.

Parameters:

uri - location of the document

Returns:

new VOElement

Throws:

org.xml.sax.SAXException

java.io.IOException

makeVOElement

public VOElement makeVOElement(java.net.URL url)
                        throws org.xml.sax.SAXException,
                               java.io.IOException

Builds a custom DOM read from a URL and returns a new VOElement based on its top-level element.

Parameters:

url - location of the document

Returns:

new VOElement

Throws:

org.xml.sax.SAXException

java.io.IOException

makeVOElement

public VOElement makeVOElement(java.io.File file)
                        throws org.xml.sax.SAXException,
                               java.io.IOException

Builds a custom DOM read from a file and returns a new VOElement based on its top-level element.

Parameters:

file - file containing XML document

Returns:

new VOElement

Throws:

org.xml.sax.SAXException

java.io.IOException

makeVOElement

public VOElement makeVOElement(DataSource datsrc)
                        throws org.xml.sax.SAXException,
                               java.io.IOException

Builds a custom DOM read from a DataSource and returns a new VOElement based on its top-level element.

Parameters:

datsrc - data source containing XML

Returns:

new VOElement

Throws:

org.xml.sax.SAXException

java.io.IOException

transformToDOM

public javax.xml.transform.dom.DOMSource transformToDOM(javax.xml.transform.Source xsrc,
                                                        boolean validate)
                                                 throws org.xml.sax.SAXException,
                                                        java.io.IOException

Gets a custom DOMSource from a generic XML Source. All elements in the returned DOM will be instances of VOElement or one of its specialist subclasses.

The clever bit is that during the parse (if xsrc is not already a DOMSource) it intercepts SAX events which indicate the start and end of any DATA events it finds so that they are not incorporated as part of the DOM. Such elements it parses directly on the basis of what it knows about items that crop up in VOTables. This keeps the resulting DOM to a reasonable size.

Parameters:

xsrc - input XML source

validate - whether to use a validating parser if the transformation needs to be done (that is, if xsrc is not already a DOMSource)

Returns:

a DOMSource representing the XML document held by xsrc The DOMSource's node will be either a VOElement or a VODocument

Throws:

org.xml.sax.SAXException

java.io.IOException

setStrict

public void setStrict(boolean strict)

Determines whether a strict reading of the VOTable standard will be enforced. Currently if strict is set to false the following standard-violating assumptions will be made:

• A FIELD or PARAM element with a datatype attribute of "char" or "unicodeChar" but no arraysize attribute will be assumed to represent a character array (arraysize="*") rather than a single-character value.

Parameters:

strict - true iff you want a strict reading of the VOTable standard

See Also:

isStrict(), STRICT_PROPERTY

isStrict

public boolean isStrict()

Indicates whether a strict reading of the VOTable standard is in effect. If it has not been set explicitly, this will return the result of isStrictByDefault().

Returns:

true if the VOTable standard is being interpreted strictly

See Also:

setStrict(boolean)

isStrictByDefault

public static boolean isStrictByDefault()

Indicates whether strict interpretation of the VOTable standard is on by default (if it has not been set explicitly). The return value will be the value of the system property named STRICT_PROPERTY, or of STRICT_DEFAULT if that is not set.

Returns:

whether VOTable strict interpretation is on by default

See Also:

setStrict(boolean)